1. Field of the Invention
This invention is concerned with means for providing a low sulfur, low pour fuel oil composition. More particularly, the invention is concerned with a fuel oil composition containing a major amount of a high pour, low sulfur, waxy residual fuel and a minor amount of a low wax, low pour, residual fuel oil, this blend having a reduced pour point relative to its components owing to the incorporation therein of a minor amount of an oil-soluble terpolymer or graft copolymer.
2. Description of the Prior Art
As is well known, residual fuel oils contain quantities of wax and asphaltic compounds which render them viscous and which sometimes interfere with practical use thereof. Particularly serious problems can be encountered in pumping residual fuel oils to a burner and in making them flow at low temperatures. Other factors to be reckoned with in regard to these oils are the facts that they behave as non-Newtonian liquids at low temperatures; exhibit variable solidifying temperatures and manifest peculiar hysteresis phenomena--all of which result in difficulties in equipment design.
One approach used in making these oils easier to handle has been to subject them to fairly lengthy and costly dewaxing procedures.
Another approach which has been suggested and tried in order to bring the viscosity of residual fuel oils to suitable levels has been to dilute or "cut" them with a major amount of lighter distillate oils. This procedure is expensive because of the considerably higher cost of the distillate oils relative to that of residual oils.
In recent years it has been recommended to incorporate additives in lubricating oils and in so-called middle distillates in order to tie in the wax present therein and to improve flow characteristics at reduced temperatures. The additives in question consist either of compounds formed by alkylating benzene or naphthalene derivatives; or, of copolymers of ethylene-vinyl fatty acid ester of a molecular weight up to 3,000 containing from 15 to 25 percent by weight of the vinyl fatty acid ester.
The main object of the present invention, accordingly, is to provide for critical blending of high pour waxy residual fuel oils with low waxy, low pour residual fuel oils to give large increases in pour reduction without employing elaborate dewaxing procedures.
An equally important object of the claimed invention is to provide a novel fuel oil blend characterized by a low sulfur content and a reduced pour point resulting from the incorporation therein of a small amount, for example, a terpolymer of vinyl acetate, ethylene and propylene or butylene.
A further object of the claimed invention is to provide a fuel oil blend which will be stable at different blend temperatures over prolonged storage times.